A passenger airbag apparatus that restrains a passenger is provided in an instrument panel of a vehicle. The passenger airbag apparatus secures in place an airbag cover provided as a portion of the outer appearance of the instrument panel and a frame-shaped body that uses a rear surface of the airbag cover as an installation surface; the frame-shaped body is then fitted with components including a retainer, airbag, and inflator. When the frame-shaped body is fixed to the rear surface side of the instrument panel, the frame-shaped body is often welded using a welding technique (such as vibration welding) since these components are made of resin (see JP, A, 2008-114747, for example).
In recent years, the instrument panel of a vehicle has sometimes been designed with an outer appearance that has an overall curved surface shape. This is in response to various factors, including the design perspective, vehicle interior layout restrictions, and to ensure various functionalities. In such a case, in locations where this curved surface shape hinders vibration operations related to vibration welding, there has been high demand to devise a structure that is conducive to vibration welding, making it possible to evenly join the areas where the airbag cover main body portion and frame-shaped body face each other. According to the above prior art, a plurality of ribs is provided to the rear surface side of the instrument panel so as to extend across the entire opening portion of the airbag cover that tears open on a tear line, making it possible to evenly join these ribs and the installation surface of the frame-shaped body facing these ribs.
The instrument panel comprises an opening portion of a plate shape that is divided by a tear line for tearing. This opening portion tears open on the tear line by the pressure imparted by the inflation load of the airbag, deploying toward the occupant. According to the above prior art, the plurality of ribs is mainly provided to the rear surface of the opening portion.